Gene Upregulation/Increased Expression in HMG-CoA Reductase

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Gene Upregulation/Increased Expression in HMG-CoA Reductase

Post by Upperninety8 » Tue Sep 30, 2014 3:21 am

So some context, I haven't taken genetics. However, in a class the other day a professor tried to differentiate the two and left me pretty confused.

From my understanding, increased gene expression will result in an increase in the protein product that a gene is coding for. Meaning that if you increased expression of a gene that codes for an enzyme, it would result in upregulation of that enzyme.

^What's wrong with my thinking on this?

If you want specifics, the discussion was on low serum cholesterol and what physiologic effects it would have. The professor (to the best of my understanding) was explaining that low serum cholesterol would result in increased LDL-Receptors but would not result in upregulation of HMG-COA Reductase (the rate limiting step of cholesterol synthesis) However, wouldn't you expect to see the body compensate for low serum cholesterol by increasing cholesterol production? And in order to increase cholesterol production you would see increased expression of HMG-COA Reductase. How is that different from upregulation of the enzyme?

I have looked around for an answer but have come up short. I read through a paper from Lipids in Health and Diseases about the topic (citation to follow), but they didn't differentiate between increased expression and upregulation. Again, my professor told us that HMG-CoA reductase would have increased expression but not upregulation in the presence of low serum cholesterol. I guess in my mind increased expression would lead to upregulation of the enzyme, and that's where I'm getting confused.


Mutungi G, Torres-gonzalez M, Mcgrane MM, Volek JS, Fernandez ML. Carbohydrate restriction and dietary cholesterol modulate the expression of HMG-CoA reductase and the LDL receptor in mononuclear cells from adult men. Lipids Health Dis. 2007;6:34.

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